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At Risk

Big Ocean, Big Challenges

From rising seas to the melting Arctic, we explain the ocean's toughest issues — and what we can do.

Eric Solomon
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Explaining Melting Sea Ice

Why does sea ice matter to you, me and everyone we know? Let's find out.

Explaining Sea Level Rise

Where is all this extra water coming from? Let's find out.

Unplug for Cleaner Air

You can make a big impact by following this easy and fun rule.

Copenhagen's Clean Harbour

How Denmark's capital turned its polluted port into the city's swimming pool.

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Eric Solomon

Cities have long treated the waterfront as a gigantic sewer and Copenhagen’s harbour was no different. When the rain poured, the sewage flowed. Ships dumped their bilges in port and shoreline factories purged industrial chemicals into the water. No one wants to live near a sewer, let alone swim in it. For years, Copenhagen’s harbour sat stinky, undeveloped and underused.

Unfortunately, a polluted port is the rule in major cities, not the exception. From oil refineries pumping toxic sludge into New York’s East River during the industrial era to athletes swimming through raw sewage during the 2016 Olympics in Rio de Janeiro’s bay, clean water has often taken a backseat to industry and development.

Some cities are making strides in cleaning up their act, but Copenhagen is ahead of the pack. In the mid-1990s, the municipality invested in a series of projects that aimed to revitalize the port.

Nearly 100 overflow channels once fed wastewater into the Danish capital’s harbour and coastlines. After building a reservoir to hold rainwater during a storm, they closed 55 channels. This severely curtailed the amount of sewage flowing into the city harbour.

Photo: Naotake Murayama / flickr

In 2003, Copenhagen’s investments bore fruit when the water was deemed safe for swimming and a free public pool opened in port. More soon opened catering to every watery preference, from paddlers to loungers to lane swimmers. Where once there had been barren contaminated shorelines, now there are public docks where hundreds clamber to take a dip on a sunny day.

After very heavy rainfall the harbour still gets a shot of sewage, but hooked-up Danes can check the water quality via phone app before taking the plunge. Cleaning up a polluted waterway isn’t easy, fast, or cheap but, as Copenhagen discovered, a new swimming hole is worth it.

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